Selective flocculation and flotation of slimes from sylvinite ores

ABSTRACT

A process for desliming sylvinite ores by a selective flocculation and froth flotation of the slimes is provided. The process involves treating the ore pulp with a high molecular weight acrylamide polymer to flocculate the slimes and then with a cationic collector for the flocculated slimes. The treated ore pulp is then subjected to froth flotation to float off the slimes.

United States Patent [191 Brogoitti et al.

[ Apr. 23, 1974 1 1 SELECTIVE FLOCCULATION AND FLOTATION OF SLIMES FROM SYLVINITE ORES [75] Inventors: William Bruce Brogoitti, Tucson,

Ariz.; Frank Peterson Howald, Sunnyvale, Calif.

[73] Assignee: American Cyanamid Company,

Stamford, Conn.

[22] Filed: Apr. 7, 1972 21 Appl. No.: 242,248

[52] US. Cl. 209/5, 209/166 [51] Int. Cl B03b 1/04, 803d 1/02 [58] Field of Search 209/5, 166; 210/44 [56] References Cited UNITED STATES PATENTS 2/1960 Williams 209/166 1/1962 Schoeld ..209/166X Primary ExaminerRobert I-Ialper Attorney, Agent, or Firm-John L. Sullivan [5 7] ABSTRACT A process for desliming sylvinite ores by a selective flocculation and froth flotation of the slimes is provided. The process involves treating the ore pulp with a high molecular weight acrylamide polymer to flocculate the slimes and then with a cationic collector for the flocculated slimes. The treated ore pulp is then subjected to froth flotation to float off the slimes.

10 Claims, No Drawings SELECTIVE FLOCCULATION AND FLOTATION OF SLIMES FROM SYLVINITE ORES This invention relates to the beneficiation of sylvinite ore. More particularly, it relates to an improvement in the beneficiation of sylvinite ore whereby the recovery of sylvite (KCl) is substantially increased. Still more particularly, it relates to a novel procedure for the removal of clay slimes from the ore whereby the loss of KCl values, normally encountered in the desliming of the ore, is substantially reduced.

It is well known that for the most efficient recovery of sylvite from sylvinite ores by froth flotation it is necessary to first remove the relatively fine, non-sylvite materials, such as clays, other silicates and the like, commonly known as slimes. Usually, this is accomplished by some type of mechanical separation. The most efficient method to date has been by means of cyclone separators. Thus, the ore pulp is passed through the cyclones and the overflow, after thicknening, discarded. By this method, however, a substantial proportion, usually from about to percent, of the sylvite values in the ore are removed along with the slimes. The sylvite thus lost in the desliming is not available for recovery in the subsequent sylvite flotation of the ore and, consequently, the sylvite recovered in the flotation step is substantially reduced. A means for avoiding this significant loss of sylvite in the desliming of the ore would, of course, be highly desirable. It is the object of the present invention to provide such a means.

In accordance with the invention, it has been found that, instead of the conventional desliming practice, the desliming of sylvinite ores can be effected, with less than about 1 percent of the sylvite values being removed with the slimes, by a process in which the pulped ore is subjected to a selective flocculation, followed by froth flotation of the slimes. Thus, in accordance with the invention, the ore pulp is treated first, with from about 0.005 to about 0.5 lbs/ton, of a high molecular weight anionic or nonionic polyacry lamide, whereby the slime particles are flocculated, and then with from about 0.01 to about 1.0 lbs/ton of a defined type of cationic agent capable of selectively floating the flocculated slimes. A suitable frothing agent is then added, air is introduced and the resulting froth containing the slimes is removed by skimming.

It has been found that with most ores, when the slimes are removed in this manner, less than 1 percent of the sylvite values of the ore are removed(or lost) along with the slimes. In certain instances, however, higher amounts of the sylvite values may be removed. In such cases, the skimmed-off froth is subjected to a cleaner flotation stage, resulting in a froth product containing the slimes and a tailing containing practically all of the sylvite removed in the initial treatment. This second tailing is then combined with the tailing from the initial slime flotation and the whole sent to a conventional sylvite flotation recovery step.

Oftentimes his the practice in the art to subject the original ore pulp to a preliminary screening and cycloning whereby a major proportion of the slimes is separated and discarded. The separated slime fraction nev' ertheless contains a significant amount of the sylvite values of the ore. However, is this slime fraction is treated by the process of the invention, a tail fraction will'be obtained which contains practically all of the sylvite values and the same may be substantially completely recovered by passing the tail fraction to the sylvite flotation step.

The process of the invention, therefore, may be advantageously applied to the original (run-of-the-mill) ore pulp or a slime fraction obtained by screening, or by hydroseparation using cyclones. It will be understood, however, that the amounts of the polymer and collecting agent used in treating such a slime fraction will be the same as that for treating the original ore pulp since the slime fraction will contain substantially all of the slime contained in the original ore.

The acrylamide polymers useful in the process of the invention include both the polyacrylamides and copolymers of acrylamide with up to about mole percent of a copolymerizable monomer, such as acrylic or methacrylic acid and their lower alkyl esters, acrylonitrile, methacrylonitrile, meth-acrylamide, vinyl alkyl ethers, styrene, vinyl chloride, vinylidene chloride and the like. Partially hydrolyzed polyacrylamides, containing up to 70 percent sodium acrylate groups, are also suitable. The polymers are soluble in saturated brine solutions and have molecular weights ranging from 500,000 to 30 million. Polyacrylamides and the copolymers of acrylamide with acrylic or methacrylic acid are generally preferred because of their commercial availability. Highly suitable commercial polymers are, for example, (1) a polyacrylamide containing less than 1 percent carboxyl groups and having a molecular weight of 12-15 million (referred to hereinafter as Polymer A); (2) a polyacrylamide containing less than 1 percent carboxyl groups and having a molecular weight of 3-5 million (referred to hereinafter as Polymer B); (3) a copolymer of 70 percent acrylamide and 30 percent acrylic acid having a molecular weight of about 2 million (referred to hereinafter as Polymer C); and (4) a hydrolyzed polyacrylamide containing 7 mole percent sodium acrylate and having an M. W. of 12-15 million (Polymer D hereinafter).

The cationic collecting agents useful in the invention are either A. condensation products of ethylene oxide with a nitrogen-containing compound selected from:

a. a long-chain (C -C primary or secondary aliphatic amine b. a long-chain (C -C alkyl guanidine;

c. a long-chain (C -C alkyl amine carbamate;

d. a long-chain (C -C alkyl guanidine salt of a long chain C -C alkyl carbamic acid;

e. a long-chain (C -C alkyl guanidine carbamate;

and

f. a long-chain (C -C alkyl amide; or

(B) a quaternary ammonium chloride having at least one long chain (C -C alkyl or long-chain acyl (alkyl- CO-) group.

The condensation products (A) are made by reacting 1 mole proportion of the nitrogen-containing compound with from 1 to 10 mole proportions of ethylene oxide, the ethylene oxide being condensed into the nitrogen compound at the amino nitrogen atom(s) thereof. Thus, for example, is the case of a primary amine (R-NH reacted with 5 moles of the ethylene oxide, the product would have the formula Since, however, the exact formulas for all of the condensation products are not known, they are not definable by a generic formula and they are, therefore, defined herein in terms of the number of moles of ethylene oxide reacted with the nitrogen compounds. It is seen, however, that products are characterized by having at least one long-chain (C -C aliphatic group attached to an amino nitrogen therein and from 1 to ethoxy groups condensed therein.

Specific examples of the condensation products are as follows:

(I) Reaction product of 1 mole of Cocoamine and 5 moles ethylene oxide (Cocoamine is a mixture of C -C alkyl amines.)

II Reaction product of 1 mole of Tallow Amine and 5 moles of ethylene oxide. (Tallow amine is a mixture of saturated and unsaturated C -C alkyl amines.)

III Reaction product of 1 mole of Tallow Guanidine with 3.25 moles ethylene oxide.

IV Reaction product of 1 mole of Tallow Amine Salt of N-Tallow Carbamate with 3.3 moles of ethylene oxide.

V Reaction product of 1 mole of the Tallow (fatty alkyl) Guanidine salt of N-Tallow Carbamic acid with 6 moles of ethylene oxide (as a 70 percent solution in aqueous isopropanol).

Vl Reaction product of 1 mole of the Tallow Guanidine salt of N-Tallow Guanylcarbamic Acid with 3 moles of ethylene oxide.

Vll Reaction product of 1 mole of Oleamide with 5 moles of ethylene oxide.

Specific examples of quaternary ammonium salt collectors are:

VIII Trimethy], Octadecyl Ammonium Chloride.

IX Dimethyl, Di-Hydrogenated Tall Oil Ammonium Chloride.

X Methyl Bis(2-hydroxyethyl) Octadecyl Ammonium Chloride.

XI N-Benzyl-N,N-Dimethyl-N-Lauramidopropyl Ammonium Chloride.

XII I N-Acetate-N,N-Dimethyl-N-Stearamidopropyl Amine. (The anion is -Cl-I CO In practicing the invention, the ore is crushed to flotation size and scrubbed in saturated brine at 70 percent solids. The pulp thus formed (or a slimes fraction thereof produced by screening and/or cycloning) is then charged to a flotation machine and diluted to about 20 percent solids with saturated brine. The machine is started and the required amount of polymer is added as a dilute brine solution thereof. After a brief period, the required amount of collecting agent is added as a dilute solution in brine. A frothing agent is then added and, after a further brief conditioning period, air is introduced. The resulting froth containing the slimes is then skimmed off.

The invention is illustrated by the following examples.

EXAMPLE 1 A A sylvinite ore assaying 37.7 percent of KC] was crushed and scrubbed for 20 minutes at 70 percent so]- ids in saturated brine. The pulped ore was then charged to a laboratory size Fagergren'flotation machine and diluted to 20 percent solids with saturated brine. The machine was then run at approximately 900 RPM and after seconds the pulp was conditioned for 15 seconds with 0.034 lbs./ton of Polymer A (supra). It was then conditioned for 15 seconds with 0.086 lbs/ton of Reaction Product V (supra) as collector agent and 0.02 lbs/ton of methyl isobutyl carbinol as frothing agent. Air was then turned on and the resulting clay froth removed by skimming over a period of 5 minutes. The pertinent data are shown in Table I.

W.l.==water insolubles As shown in Table I, the separated clay slimes contained only 0.9 percent of the KC] originally present in the ore, 99.1 percent being retained in the ore pulp (Sand). 7

B For purpose of comparison, a desliming of a similar ore, assaying 42.4 percent KC], was mechanically deslimed as follows: 1200 g. of ore was scrubbed with 425 cc. of brine for 5 minutes in a laboratory Denver agitator at 900 rpm. The scrubbed ore was then transferred to a 4,000 cc. graduate cylinder. After diluting to 4,000 cc. with brine, the cylinder was up-ended three times. After 2 minutes settling time, the supernate was siphoned off onto a IOO-mesh screen. The residual pulp was then diluted to 2000 cc. with brine and up-ended 3 times. After settling l )6 minutes, the supernate was siphoned off onto the lOO-mesh screen.

The lO0-mesh material on the screen was then combined withthe residual (deslimed) pulp. Table I! shows the pertinent data for the desliming effected in this manner.

TABLE II Analysis Distribution KC] W.l. KC!

Feed 42.4 6.9 100.0 Sand 43.4 0.8 86.6 Slirnes 36.5 39.7

It will be seen that in this case 13.4 percent of the original KCl content of the ore is separated with the slimes leaving only 86.6 percent in the ore pulp (Sand).

EXAMPLE 2 As has been indicated hereinabove, the most efficient desliming of sylvinite ores has been accomplished by means of cyclones. Thus, l00 mesh ore obtained by- TABLE [II Analysis Distribution KCl 72 W.I. KCl

Feed (Hydroseparator 52.5 14.0 100.0

Underflow) Cyclone Underflow 53.5 10.7 43:3 (to sylvite float) Cyclone Overflow 51.7 26.6 56.7

6 From the data in Table VI, it will be seen that in each case the slimes were separated from the sand with a very high proportion of the KCl being left in the sand fraction.

For purpose of comparison, a sample of the hydro- W l i separator h i taken from the Same f e as l. A method for desliming a sylvinite ore comprising that Shown Tehle 11.1, was treated y the deshmmg (l) conditioning the ore, pulped in saturated brine, Process of e lhvehtleh, p y g of with (a) from about 0.005 to about 0.5 pounds per ton Polymer A, 0f Reaetl0h Preduet V p of an acrylamide polymer and then with (b) from about and of methyl lsobutyl The restllts 10 0.01 to about 1.0 pounds per ton of a cationic collector are glveh Table for the slimes. (2) subjecting the conditioned ore pulp TABLE IV to froth flotation and (3) removing the floated slimes;

said cationic collector being (A) a condensation product of from 1 to 10 mole proportions of ethylene oxide Analysls Dlstrlbunon 5 %KC| KC! wlth 1 mole proportlon of a nltrogen-contalnlng com- F d H d 58 I2 8 pound selected from the group consisting of (a) a longi f ig loo'o chain alkyl primary or secondary amine, (b) a long- Slime Float Tail 05.5 3.2 91.4 chain alkyl-substituted guanidine, (c) a long-chain Pmduct alkyl amine carbamate, (d) a long-chain alkylsubstituted guanidine salt of a long-chain alkyl car- A comparison of Tables I and 11 shows that cycloning f (e) a longchain atkyl'sutsmuted atkyl makes a simple size separation, whereas the process of guamdme carbamate and t) a 'f alkyl ei the invention provides a selective separation (flotation) or (B) a quaternafy ammomutn salt havmg a longcham of the water-insoluble materials away from the sylvite alkyl or long'cham 3Cyl minerah 2. The method of claim 1 whereln the acrylamlde polymer is a polyacrylamide containing less than 1 per- EXAMPLES cent carboxyl groups and having a molecular weight of Further slime flotations of sylvinite ores were con- 12-15 mlthohducted (Examples 3-l4) after the fashion of Example The methd of claim 1 wherein the 't' l, employing 0.05 lbs/ton of Polymer A, and 0.20 P y 18 a p y e of 70 Percent acrylamlfie and lbs./ton of collecting agents l-xll, identified herein- 30 p t acrylic acid havmg a molecular Weight of above, except that in Example 1 1 only 0.15 lbs./ton of 'about 2 million. Collector [X was used. The pertinent data with respect he ethod 0f Claim 1 wherein the acrylamlde tothe e.flctat ons teshqw in a le 1190 is 8. 1 19152 18 ElZ9XL3EiE99Elh1Ei TABLE v Feed, percent Sand, percent Slimes, percent Analysis Distri- Analysis Distri- Analysis Distri' ution, bution, bution, Example number Collector KCl w.1. K01 K01 w.1. KCl KCl W.I. KCl

As will be seen from Table V, in every instance, only about 7 mole percent sodium acrylate and having a moa small percentage of the KC] values were removed lecular weight of 12-15 million. along with the slimes. 5. The method of claim 1 wherein the cationic colleci tor is the reaction product of 6 mole proportions of eth- EXAMPLES 15-18 ylene oxide with l mole'proportion of the tallow guani- A further series of desliming tests on sylvinite oredine salt of N-tallow carbamic acid. M (Examples were carried Out mploying Poly- 6. The method of claim 1 wherein the cationic collecmers A, B, C and D in conjunction with Collector V.'{ tor is the reaction product of 5 mole proportions of eth- Ths 9 012292940 re 8.1!?919. I bleylex1998 9419. with 3.199 8 P QRQFF W fsti v min TABLE VI 1 Feed, percent Sand, percent Sllmes, percent Polymer Collector Analysis Distri- Analysis Distrl- Analysis Distri- Lbs./ Lbs./ ution, bution, bution, Example number No. ton N0. ton KCl W.I. K01 K01 W.I. K01 K01 W.I K01 0.040 v 0.092 38.4 7.91 43.1 0.95 97.9 0.3 55.7 2.1 0.045 v 0.090 41.2 7.40 100 42.5 1.99 92.0 30.3 55.9 7.4 0.043 v 0.086' 39.5 7.04 100 42.0 2.00 99.1 42 032 0.9 0.044 v 0.088 39.0 7.04 43.3 2.01 90.5 4.3 3.5

. 7 8 7 JTh method of claim T whereirithe cationic collec- 9. The wherein the cationic collector is the reaction product of mole proportions of ethtor is trimethyl octadecy] ammonium hl id ylene oxide with 1 mole proportion of tallow amine.

8. The method of claim 1 wherein the cationic collector isthe reaction product of 5 mo l e proportions of eth- 5 ylene oxide with 1 mole proportion of oleamide.

10. The method of claim 1 wherein the cationic collector is methyl bis(2-hydroxyethyl)octadecyl ammomum chloride. 

2. The method of claim 1 wherein the acrylamide polymer is a polyacrylamide containing less than 1 percent carboxyl groups and having a molecular weight of 12-15 million.
 3. The method of claim 1 wherein the acrylamide polymer is a copolymer of 70 percent acrylamide and 30 percent acrylic acid having a molecular weight of about 2 million.
 4. The method of claim 1 wherein the acrylamide polymer is a hydrolyzed polyacrylamide containing about 7 mole percent sodium acrylate and having a molecular weight of 12-15 million.
 5. The method of claim 1 wherein the cationic collector is the reaction product of 6 mole proportions of ethylene oxide with 1 mole proportion of the tallow guanidine salt of N-tallow carbamic acid.
 6. The method of claim 1 wherein the cationic collector is the reaction product of 5 mole proportions of ethylene oxide with 1 mole proportion of cocoamine.
 7. The method of claim 1 wherein the cationic collector is the reaction product of 5 mole proportions of ethylene oxide with 1 mole proportion of tallow amine.
 8. The method of claim 1 wherein the cationic collector is the reaction product of 5 mole proportions of ethylene oxide with 1 mole proportion of oleamide.
 9. The method of claim 1 wherein the cationic collector is trimethyl octadecyl ammonium chloride.
 10. The method of claim 1 wherein the cationic collector is methyl bis(2-hydroxyethyl)octadecyl ammonium chloride. 